1. Field of the Invention
The present invention relates generally to an assembly for use in transporting devices to sites of wellbores. More particularly, this invention relates to a platform such as a trailer for transporting coiled tubing and an injector assembly to a wellhead, and for aiding in the alignment of the injector assembly at a wellhead, for the subsequent injection of coiled tubing into a wellbore.
2. Description of the Related Art
Coiled tubing may better suited for performing various downhole tasks, such as many reservoir stimulation techniques, as opposed to using solid drill string. For example, it is known to attach a downhole tool, such as a straddle packer, to coiled tubing and run the packing device downhole until the desired zone is reached. Once positioned, a well treatment such as a fracing operation or other stimulation operation may be accomplished, e.g. For example, a fluid such a fracing proppant or sand slurry may be forced from surface, through the coiled tubing string and into the zone straddled by the packer.
As an example of an operation using coiled tubing and as shown in FIG. 1, a packer P has been lowered via coiled tubing 10 into a wellbore W to force a fluid into zone Z2, while preventing fluid communication with the zone Z1 above zone Z2.
To inject coiled tubing into the wellbore, an injector assembly having an injector head typically is attached to a wellhead at surface of a wellbore. In a typical coiled tubing operation, coiled tubing is injected downhole through a wellhead by a coiled tubing injector. The injector operates to grab the coiled tubing from the spool and inject the coiled tubing into the wellbore via facing chain drives on the injector.
Generally, a Blow Out Preventor (“BOP”) is used as a safety device when performing a downhole operation. The BOP is customarily used in downhole operations to control the well. For instance, if a negative differential pressure between the hydrostatic pressure of the coiled tubing fluid and the formation pressure exists, fluid may tend to escape to surface. Although various configurations and models of BOPs are known, their function is the same: to take over should the primary well control fail. Thus, when running coiled tubing, an injector assembly having a BOP is may be utilized to inject the coiled tubing off the spool and into the wellbore.
Generally, to attach the injector assembly with a BOP to a wellhead, it is known to utilize at least two trucks to align the BOP and the injector with the wellhead. For instance, in the system of FIG. 1, a first truck 1 pulling a trailer 2 is utilized for transporting the coiled tubing spool 20, the BOP 60, and the injector head 50 to the wellhead 1000. The BOP 60 and the injector head 50 may be stored separately on the back of the truck. Or the BOP 60 and injector head 50 may be preassembled and pre-stabbed with the coiled tubing 10 to minimize assembly time at the wellhead 1000. The injector 50 may comprise a gooseneck 55 as shown in FIG. 1 as an aid to align the coiled tubing 10 from the spool 20 into the injector 50.
A second truck 3 may be utilized to transport a second trailer 4 to the site. The second trailer 4 may comprises a crane having a boom 30, which may include a boom with telescopic arms. Such telescoping cranes are known to be commercially available from Furukawa UNIC Cranes from Japan or National Crane Corp. of Shady Grove, Pa., and are known to have a maximum capacity of over 66,000 pounds (29.9 Metric Tons) and a vertical reach of 170 feet (50.9 meters).
Further, when performing a some operations, a third truck or even more trucks may be utilized to accomplish the operation, for example.
The first truck 1 and the second truck 2 are positioned in relatively close proximity to the wellhead 1000 via the truck driver pulling as close as possible to the wellhead 1000. Once both the first truck 1 with trailer 2 and the second truck 3 with trailer 4 are at the wellhead, these trucks are aligned such that the boom 30 on the trailer 4 may be connected to the injector assembly to remove the injector assembly with the injector 50 and the BOP 60 from the first truck 1 and place the BOP 60 on the wellhead 100.
The BOP 60 is manually connected to the end of the arm of the boom crane 30 via a cable 40. Once the BOP 60 is set, the boom crane 30 on the trailer 4 of the second truck 3 may operate to remove the injector head 50 from a rack on the trailer 2 of the first truck 1 to connect the injector head 50 to the BOP 60.
In some cases, the injector 50 is preassembled to the BOP 60, and the injector is pre-stabbed with the coiled tubing 10 during transport. The boom 30 of the crane is attached to the injector assembly via cable 40. The boom crane 30 lifts the injector assembly via a cable 40, and an operator O at surface connects the BOP of the injector assembly to the wellhead 1000. During this connection period, the BOP and the injector assembly may sway from the cable 40 in the wind, a considerable distance above the operator O, the injector assembly weighing over 5000 pounds. It is desirable to provide a more positive connection means such that the injector assembly would be less likely to sway in the wind, which also would improve the safety of the setting operation.
The crane with the boom 30 may have a boom with telescopic arms. Further, the crane may rotate 360 degrees with respect to the bed of the trailer 4. Further, the boom itself may rotate with respect to the plane of surface, from zero degrees (i.e. horizontal) to ninety degrees (i.e. perpendicular) to the trailer.
Once the BOP 60 and injector 50 are attached to the wellhead 100, the coiled tubing 10 is injected from the spool 20 into the wellbore 100. The underground operation, such a running a straddle packer P and performing a well treatment as described above, may be performed.
Various factors may further complicate the alignment of the injector assembly with the wellhead 1000. As stated above, the BOP 60 and the injector 50 may hang or “dangle” from the boom 30 of the crane via the cable 40. Further complicating the procedure is the fact that each the BOP 60 and the injector 50 may weigh in excess of 5000 pounds, with the injector assembly hanging from the cable over thirty feet in the air, the alignment with the wellhead may be difficult. Thus, it is desired that an assembly with improved safety and security for performing the setting operation be provided. I.e. with these injectors and BOPs weighing over 5000 pounds, extending over thirty feet m the air, it is desirable to have control of the movement of the injector to improve the safety of the operation.
Further, in these prior art system, the two drivers for the first truck 1 and second truck 3 attempt to align the trailers 2 and 4 respectively proximate the wellhead 1000. Depending on the drivers' abilities, this alignment operation may prove less than ideal, and may include trial an error, thus increasing the rig up or setting time.
Further, in many some instances the wellhead is not perpendicular with surface. In others, the surface itself is not perfectly horizontal. Further, wind may act to sway the injector assembly as described above. These conditions, inter alia, may cause complications in setting the injector at the wellhead, which, in turn, may increase the rig-up time.
Similarly, when it is desired to remove the coiled tubing from the wellbore, the crane on the second truck may be used to remove the injector assembly with the BOP 60 from the wellhead 1000 via a cable 40. The injector 50 with the BOP 60 may be stored on trailer 2 of the first truck 1, in a dissembled or pre-stabbed/pre-assembled fashion as described above.
It would be advantageous to provide a system, which more positively controlled the movement of the injector assembly for alignment with the wellhead.
Other systems have been developed in an attempt to reduce the amount of operator intervention in the setting of the injector assembly on the wellhead 1000. For example, it is known to utilize a mast crane system for setting up a wellbore intervention. Such a system is the Mast Coiled Tubing Unit, known to be utilized by BJ Services Company, of Houston, Tex. With a mast unit, a self-erecting mast is brought to the wellhead by one truck. The vertical supports of the mast are positioned over the wellhead by properly positioning the trailer on the first truck with respect to the wellhead. Once in the desired location, the vertical supports contact the surface and the mast elevates the injector from eight to forty-eight feet above surface. The mast is attached to a trailer and is erected at the wellbore. Such a mast unit structurally supports the injector. As such, no crane-supported overhead load exists. Thus, fewer overhead lifts are required, as the BOPs are transported on the unit and hydraulically lifted into place.
With a mast unit, a miniature drilling mast is attached to the back of a trailer. The mast is attached in such a way that it may move vertically with respect to the trailer. Some mast units provide little adjustment with respect to the location near the wellhead. Thus, the truck must be driven relatively close to the wellhead for proper alignment. The mast unit is comprised of two vertical uprights with the injector traveling vertically within these uprights. These uprights of the mast are designed to be folded back onto the trailer, and may be placed vertically when it is desired to place the injector on the wellhead.
In some mast systems, alignment with the wellhead is provided by driving the truck around to properly position the mast with respect to the wellhead. Further, two trucks are typically utilized with the mast systems; one for the mast, and one for the coiled tubing and injector assembly. In some mast units, the injector and the BOP are affixed to the mast assembly during transportation and operation. In some mast units, the tubing reels are provided on the same trailer. Regardless, alignment may prove problematic with some of these mast units.
Thus, it is desirable to provide an apparatus for transporting an injector assembly, which may include a coiled tubing injector and a BOP, to a wellhead, and to facilitate the placement of the injector assembly on the wellhead. It is desirable that such an apparatus be quickly and positively aligned with the wellhead. It is desirable that such a system positively provides contact between the injection assembly and the wellhead such that the assembly does not dangle overhead of operators from a cable. It is further desirable that the apparatus allow the BOP and injector to be pre-stabbed with coiled tubing during transport to minimize rig-up time at the site. It is desirable to minimize the equipment and manpower required at the wellbore. Thus, it is desirable that the BOP be preassembled with the injector head to minimize rigging or set up time. It if further desirable to remove some of the human interaction, to reduce the number of operators and equipment at the wellhead, and to improve the placement accuracy of the injector assembly.
Thus, it would be desirable to provide a coiled tubing injector head and a BOP attached to a boom that can extend the assembly from a trailer to a wellhead for proper alignment. Such an assembly may decrease the rig-up and rig-down times of prior art system.
The present invention is directed to overcoming, or at least reducing the